Optimization and reaction kinetics analysis for phosphorus removal in struvite precipitation process

As a promising strategy to remove and recover phosphorus from wastewater, optimization of the struvite (MgNH₄ PO₄ .6H₂ O) precipitation parameters is required to achieve desirable phosphorus removal efficiency. To tackle the challenges upon the precipitation optimization methods as three-level full factorial designs, and central composite design as well, Box-Behnken design was implemented to optimize different reaction parameters for phosphorus removal and recovery during struvite precipitation in the current study. Moreover, the reaction orders and the rate equation were all determined to reveal the reaction kinetics parameters of struvite precipitation. The results showed that the optimal operating parameters of pH, Mg/P ratio and N/P ratio were 9.82, 1.45, and 4.00, respectively, by which more than 95% of phosphorus removal efficiency could be achieved. In addition, it was found that pH and pH/(N/P) had the most influence on phosphorus removal efficiency among different individual factors and interactive items, respectively. The partial orders of PO₄ -P, Mg²⁺ , and $$ in kinetic rate equation were determined as 1.586, 0.930, and 1.236 while the rate constant k was 0.0167 ± 0.0014 mM^-2.752 per minute by differential method. PRACTITIONER POINTS: Different reaction parameters were optimized by Box-Behnken design. pH and pH/(N/P) had the most influence on phosphorus removal efficiency among different individual factors and interactive items. The reaction orders and the rate equation were all determined to reveal the reaction kinetics parameters.